Mercapto- or alkylthio-substituted menthenones

ABSTRACT

There are provided novel mercapto- or alkylthio-substituted oxo-terpenoids having 10 carbon atoms in the terpenoid skeleton. These novel compounds may be acyclic monocyclic or bicyclic. The novel compounds are useful as odorants particularly, but also for producing aromas, e.g. of a vegetable note.

RELATED APPLICATIONS

This is a division of application Ser. No. 69,457 filed Sept. 3, 1970.

This application claims priority from Swiss application 13748/69 filedSept. 10, 1969.

FIELD OF THE INVENTION

Novel aromatizing agents

SUMMARY OF THE INVENTION

The present invention is concerned with new mercapto- oralkylthio-substituted terpenoids of the general formula ##SPC1##

Wherein R¹ represents hydrogen or together with R⁴ represents a C--Cbond,

R² represents hydrogen or together with R⁶ represents adimethylmethylene group, or, when R⁶ is isopropyl, together with R⁵represents a C--C bond,

R³ represents hydrogen or together with R⁶ represents adimethylmethylene group,

R⁴ represents hydrogen or together with R¹ represents a C--C bond,

R⁵ represents hydrogen or, when R⁶ signifies isopropyl, together with R²represents a C--C bond,

R⁶ represents isopropyl or together with R² or with R³ represents adimethylmethylene group,

R⁷ represents methyl,

X represents a C--C double bond taking the place of a C--C single bond,

m = 0 to 2,

Y represents oxo bound to a primary or secondary C-atom and Z representsmercapto or lower alkylthio located in the β-position to the carbonylfunction,

Provided that when R², R³ and R⁵ represent hydrogen, R⁶ representsisopropyl, R⁴ together with R¹ represents a C--C bond, Y is β to thecarbon atom bearing the substituent R⁷, m=O, Z is α to the carbon atombearing the substituent R⁵ and β to the carbon atom bearing thesubstituent R³, then Z represents alkylthio, their use as odorantsand/or flavourings, as well as a process for their manufacture.

The above formula I includes mercapto- or alkylthio-substituted acyclic,monocyclic or bicyclic monoterpenes each containing a carbonyl group,the mercapto or alkylthio substituent Z being located in the β-positionto the carbonyl function.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Formula I, as also all other formulae appearing in the description andthe claims, is meant to include all stereoisomers.

The above formula I includes the compounds of the following generalformulae as sub-groups ##SPC2##

The compounds of formulae I-1 and I-2 claiming particular interest.

In formulae I-1 to I-5, X, Y, Z and m have the significance statedabove.

The compounds I-1 are acryclic acyclic have a carbon skeleton like, forexample, citral or tagetenone. The compounds I-2 are monocyclic and havethe p-menthane skeleton. The compounds I-3, I-4 and I-5 are bicyclic anddisplay the skeleton of pinane, thujane or carane.

By lower alkylthio in the sense of the above definition are meantalkylthio residues the alkyl portion of which is straight-chain orbranched and preferably contains up to 5 C-atoms; examples of such alkylresidues are: methyl (preferred) ethyl, n-propyl, iso-propyl, n-butyl,sec. butyl, tert. butyl, amyl, etc.

The double bonds represented in the above formula I by X can be locatedin any position of the molecule, thus, for example, in the ring and/orin the side-chain in cyclic systems. These optionally present doublebonds are located between two adjacent C-atoms which are bound to otheratoms solely by single bonds.

A primary C-atom in the sense of the above definition is present in thegroup --CH₃, a secondary C-atom in the group --CH₂ --.

The new terpenoids of general formula I are distinguished by specificaroma and/or odorant properties, especially by berry, spice andvegetable notes, for example in combination with the underlyingterpenoids. They can accordingly be used for the aromatisation of foodsand delicacies as well as of drinks or as odorants for the manufactureof odorant compositions such as perfumes, or can be used for perfumingtechnical products, for example, solid and liquid detergents, syntheticwashing agents, aerosols or cosmetic products of all kinds (e.g. soaps).These compounds can be used in perfumery because of their intensivegreen notes. The compounds with Z equal to --SH are distinguished byparticularly good tenacity. The odorant compositions utilizing thesenovel compounds, for example perfumed products, can contain a wideproportional range thereof, from 0.005 to 5.0% by weight may be used.

It is to be understood that the scope of the present invention does notinclude naturally occurring compounds of general formula I.

The novel compounds of formula I can be used in a wide variety ofaromatized products. Because of their berry-like aroma properties, thesecompounds can be used for producing aroma in foods (e.g. milk drinks,yoghurt, etc.), in delicacies (e.g. confectionery products such asbonbons, soft ice, etc. and in drinks (e.g. mineral waters). They canalso be used as aroma enhancers for enhancing the aroma of vegetable,soup and snack food aromas where cabbage-like or onion like aromas areespecially desired. Their marked flavourous qualities make use in smallconcentration possible. A suitable dosage comprises the range of 0.01ppm to 100 ppm, preferably of 0.1 ppm - 1 ppm, in the finished product.

The new compounds of general formula I can be obtained in accordancewith the invention by reacting a compound of the general formula##SPC3## wherein R to R⁷, X and Y have the above significance and n = 1to 3, a double bond represented by X being located in the α,β-positionto the carbonyl function or being isomerisable into this position, witha compound HZ (wherein Z signifies the same as above) in the presence ofa base under anhydrous conditions, provided that where R² and R³ arehydrogen, R⁴ together with R¹ represents a C--C-bond, Y is β to thecarbon atom bearing the substituent R⁷, R⁵ where present is hydrogen andR⁶ is isopropenyl or isopropylidene, n = 1, then HZ is a loweralkylmercaptan.

As bases there come into consideration, for example: inorganic bases,for example alkali metal hydroxides such as sodium hydroxide orpotassium hydroxide, alkaline earth hydroxides such as, for example,calcium hydroxide, organic bases, for example amines such as alkylamines(e.g. diethylamine or triethylamine), heterocyclic amines such aspiperidine etc.

By a double bond isomerisable into the α,β-position to the carbonylfunction is meant that double bond in the molecule which is capableunder the influence of bases at elevated temperature of migrating intothe desired α,β-position from another position (e.g. β,γ-position).

The reaction of the starting compounds of general formula II in thepresence of the said bases is expediently effected in the presence of asolvent. Suitable solvents are, for example, alcohols such as alkanols(e.g. methanol, ethanol, isopropanol, ethanol being preferred), orethers such as diethyl ether (preferred), or diisopropyl ether.

However, if desired one can also work in the absence of a solvent,especially when the starting material of formula II is brought toreaction with a lower alkylmercaptan. The reaction temperatureexpediently lies between about 0°C and 100°C; a range between about 40°and 60°C is preferred. The duration of the reaction depends on thereaction temperature. For example it amounts to about two hours for areaction temperature of 40° to 60°C.

The reaction of the present invention can also be initiated by theprovision of a free radical initiator, suitably ascaridol or α,α'-azobis isobutyronitrile.

The reaction can be carried out at normal pressure or expediently atelevated pressure (e.g. 10 atm.), since the reaction proceeds withreduction in volume.

The proportion of the starting compound of general formula II to thesulphur compound HZ can be varied within wide limits; preferably, atleast 1 mol of sulphur compound HZ is used per mol of starting compoundII. The sulphur compound HZ can, however, also be used in excess.

The reaction of the starting compound II with the sulphur compound HZ isexpediently initiated by treating the starting compound II or thesolution of this starting compound in an anhydrous solvent with thesulphur compound HZ in the presence of a base (which can be added assuch or dissolved in one of the above-named solvents) at a temperaturebelow the boiling point of the sulphur compound HZ and heating themixture to the reaction temperature in a suitable pressure vessel.

New asymmetric centres can result by the reaction of the startingcompound II with the sulphur compound HZ, and consequently the reactionproduct can be obtained in the stereoisomeric forms thereby possible.

The reaction product can be isolated from the reaction mixture accordingto conventional methods; for example, by distilling off the solvent, ifnecessary, filtration of elementary sulphur which was formed from theresidual mixture and fractional distillation, by which means the productcan be separated from unreacted starting compound II.

In the following Examples the temperatures are stated in degreescentigrade.

EXAMPLE 1

15.2 g of piperitone are dissolved in 30 ml of absolute ether andtreated with 1.0 g triethylamine. The solution is cooled to ca -75°. Atthis temperature, a total of 5 ml of hydrogen sulphide is condensed inin the course of an hour, the solution initially colouring yellow andlater depositing a red-yellow precipitate. After completed H₂S--condensation, the reaction product is rapidly transferred into anautoclave, rinsed with 50 ml of absolute ether and allowed to stand for29 hours. The pressure rise during the gradual heating to roomtemperature is very slight, so that a pressure-resistance of theapparatus of 10 atm. is sufficient. The solution is thereupon filteredand concentrated. The residue (16.9 g) is fractionally distilled invacuum. After removal of 7.8 g of unreacted piperitone there are thusobtained 1.6 g of p-menthane-1-thiol-3-one of boiling point 57°-59°/0.05mm Hg, n_(D) ²⁰ 1.4932, in the form of two stereoisomers in the ratio1:4. (The cis-p-methane-1-thiol- 3-one can be separated from thetrans-p-menthane-1-thiol-3-one gas-chromatographically).

Odour of the product: sulphurous, minty, reminiscent of rhubarb, butalso suitable for cassis and blackberry notes.

EXAMPLE 2

15 g of carvone are treated with a solution of 1 g of KOH in 100 ml ofabsolute ethanol. H₂ S is condensed into the solution, cooled to -75°,until ca 20 ml of H₂ S are condensed. After standing overnight in anautoclave at room temperature, the mixture is heated to 50° for 2 hours(in so doing, the pressure rises to 8.5 atm.), then cooled, taken up inether, the ethereal solution washed with saturated NaCl solution, driedand concentrated. The residue (14.3 g) is fractionally distilled invacuum. The distillate (6.3 g) of boiling point 77°-78°, n_(D) ²⁰ 1.5248to 1.5229, contains, besides ca 10% of unreacted starting material, amixture of stereoisomeric p-menth-8-ene-6-thiol-2-ones in the ratio ofca 1:1:1.

Odour: Green with sulphurous note, reminiscent of thyme and roastonions.

EXAMPLE 3

15.2 g of citral (mixture of geranial and neral) are dissolved in 50 mlof absolute ether and treated with 1 g of triethylamine. The mixture iscooled to -70° and 10 ml of hydrogen sulphide are condensed in. Afterdecanting into a pressure vessel, the reaction mixture is allowed tostand overnight at room temperature and then it is heated to 50° for 2hours. After cooling and removal of the ether, in the residue, only alittle citral can still be detected besides the reaction productobtained.

Odour: intensive, long-lasting, reminiscent of rhubarb.

EXAMPLE 4

15.2 g of pulegone are treated with 0.5 ml of triethylamine and cooledto ca 0° by means of an ice-common salt mixture. With stirring, methylmercaptan in excess is condensed into the mixture and, aftercondensation of 200% of the calculated amount, the mixture istransferred into an autoclave. After standing overnight at roomtemperature, the reaction mixture is heated to 50° and, after cooling ofthe autoclave, the reaction product immediately distilled in vacuum. 9.8g of 8-methylthio-p-menthan-3-one are obtained as a clear liquid withpleasant odour reminiscent of peppermint, geranium and caraway, boilingpoint 72°-73°/0.15 mm Hg, n_(D) ²⁰ 1.4982. The yield amounts to 73% ofthe theory based on reacted pulegone. The two stereoisomeric compounds8-methylthio-cis-p-menthan-3-one and 8-methylthio-trans-p-menthan-3-oneobtained can be separated gas-chromatographically.

EXAMPLE 5

15.2 g of piperitone and 0.5 g of triethylamine are cooled to -5°. 15 mlof methyl mercaptan are condensed in with stirring. The mixture istreated and worked up as in Example 4. By fractional distillation,unreacted piperitone is distilled off from the reaction mixture, and the1-methylthio-p-menthan-3-one enriched to 95% content (boiling point88°/0.1 mm Hg, n_(D) ²⁰ 1.4990). The yield amounts to 6.2 g or 48% ofthe theory, based on reacted piperitone. The odour of the product isreminiscent of dill and caraway as well as of boiled white cabbage.

EXAMPLE 6

15.0 g of carvone are mixed with 0.5 g of triethylamine. 20 ml of methylmercaptan are condensed in this mixture at room temperature. Afterstanding overnight in the autoclave, the mixture is heated to 50°C for afurther 2 hours. After removal of the excess methyl mercaptan, thereaction product is fractionally distilled in vacuum. After a smallfore-run of unreacted carvone, there are obtained 14.9 g of6-methylthio-p-menth-8-en-2-one in the form of a mixture of two isomersin the ratio 1:4 (boiling point 105°-107° 10.2 mm Hg, n_(D) ²⁰ 1.5067),corresponding to a yield of 78% of the theory. The odour of the mixtureis reminiscent of boiled white cabbage with a caraway and onion peelnote.

EXAMPLE 7

15. g of citral and 0.5 of triethylamine are treated with methylmercaptan as described in Example 6. After removal of the excess pointmethyl mercaptane, there is obtained a practically citral-free crudeproduct (16 g) which after distillation yields, besides a polymericresidue, 10.4 g of 3,7-dimethyl-3-methylthio-6-octenal, corresponding toa yield of 52% of the theory (boiling poin 82°-84°/0.2 mm Hg, n_(D) ²⁰1.4961). The odour of the compound is reminiscent of kohlrabi andcauliflower with a slight citral note.

EXAMPLE 8

Into a suitable autoclave there are charged 9.0 g of 3-caren-2-one, 0.3g of triethylamine and 4 drops of ascaridol. The autoclave is cooled to-20° and 10 ml of methylmercaptan distilled thereinto. The autoclave issealed permitted to stand overnight at room temperature and subsequentlywarmed to 50°C for 2 hours. The reaction mixture is fractionallydistilled to yield 4-methylthio-2-carone (2.8 g) in the form of 2stereoisomers having a boiling point of 80°-85°C at 0.1 mm, n_(D) ²⁰1.5210.

The odor of the compound is green and earthy. The resulting aroma isvegetable like and is also reminiscent of the aroma of the tonka bean.

EXAMPLE 9

In accordance with the procedure of Example 7 verbenol is reacted withmethylmercaptan to yield 1-methylthioverbanone, boiling point 70° at 0.1mm Hg, n_(D) ²⁰ = 1.5080 (product of 70% purity).

EXAMPLE 10

In accordance with the procedure of example 7 myrtanal is reacted withmethylmercaptan to yield 2-methylthio-myrtanal, boiling point 76° at 0.3mm Hg, n_(D) ²⁰ = 1.5170. This product contains as an impurity 10% of aby-product. The aroma of the product is leek-like and is reminiscent ofcabbages and onions. The undertone is woody and green.

EXAMPLE 11

In accordance with the procedure of Example 8 car-3-en-5-one is reactedwith methylmercaptan by heating the reaction mixture in a suitablepressure-vessel for 3 hours to yield 3-methylthio-caran-5-on, boilingpoint ca 70° at 0.5 mm Hg, n_(D) ²⁰ = 1.5224.

The odor of the compound is reminiscent of garlic and shallots and has afainter smell of rhubarb and vegetables. As side notes of the aroma thearoma of balsam, spices and smoke can also be smelt.

EXAMPLE 12 Odorant Composition Having a Lavender Note

    Parts by Weight:                                                              ______________________________________                                        50      6-Mercapto-p-menth-8-en-2-one 10% (in PDE)                            100     Spanish Wood Oil                                                      450     Lavender Oil Mont Blanc                                               200     Linalyl acetate                                                       50      Linalool                                                              50      p-tert-Butyl-cyclohexyl-acetate                                       5       Coumarin                                                              25      Cinnamyl alcohol synth.                                               5       Undecylenaldehyde 10% (in PDE)                                        25      Terpineol                                                             85      Benzyl alcohol                                                        5       1,1,4,4-Tetramethyl-6-ethyl-7-acetyl-1,2,3,4-                                 tetrahydronaphthalene                                                 1050                                                                          ______________________________________                                         PDE = diethylphthalate                                                   

The added 6-mercapto-p-menth-8-en- 2-one enhanced the diffusion andstrengthened the floral impression of the composition.

EXAMPLE 13 Eau de Cologne CompositionParts byWeight:______________________________________256-Mercapto-p-menth-8-en-2-one 10% (in PDE)400 Bergamotte oil Reggio200Italian Lemon oil200 Californian Orange oil35 Neroli oil synth.5Peppermint oil italo-Mitch. rect.25 Lavender oil Mont Blanc10Methylnaphthylketone cryst.50 Linalyl acetate20 Citral B pure10 C₁₀-Aldehyde 10% (in PDE)10 1,1,4,4-Tetramethyl-6-ethyl-7-acetyl-1,2,3,4-tetrahydronaphthalene5 p-tert-Butyl-alpha-methylhydrocinnamaldehyde30Nerolidol1025______________________________________

The 6-mercapto-p-menth-8-en-2-one added as a solution of its crystallineadduct considerably enhanced the diffusion and rounded the bouquet off.

EXAMPLE 14 Aromatisation of a powdered soup

A neutral testing powdered soup preparation was prepared according tothe following recipee.

    ______________________________________                                        18%        NaCl                                                               12%        Sugar                                                              10%        Sodium glutamate                                                   10%        hydrolyzed vegetable proteins                                      50%        corn starch                                                        100%                                                                          ______________________________________                                    

For the preparation of 1 liter neutral-testing soup 45 g of thispreparation are necessary. The addition of 2,7-3,5g6-methylthio-p-menth-8-en-2-one per 100 l of soup imparted to theneutral-testing soup a pleasant onion and leek-taste.

EXAMPLE 15 Aromatisation of mashed potatoes

Neutral testing mashed potatoes are prepared by mixing of

15 g potato flakes and

85 g water.

The addition of 3-4 g of 6-methylthio-p-menth-8-en-2-one per 100 kg ofmashed potatoes imparted to the product a leek-taste; the thiolone(1,5-2 g) in 0,5 % NaCl (100 l H₂ O) imparted to such solution apredominant note of horseraddish and onion.

What is claimed is:
 1. p-Menthane-1-thiol-3-one. 2.8-Methylthio-p-menthan-3-one.
 3. 1-Methylthio-p-menthan-3-one.